It’s the Thursday before the long Fourth of July weekend, and people all over the city are scurrying to finish work and prepare for the holiday. But at the Grand Central branch of Equinox, a group of particularly fit men and women cram up against a wall, waiting for the boot camp-style Tabata 2010 class to begin. After a mad dash for prime spots in the room, they settle in shoulder-to-shoulder; a handsome young Latino with a tattoo, next to a clean-cut financial guy, next to a cute blonde with super-toned legs.

“C’mon work, work! Work to the beating rhythm and the joy,” urges instructor Angel Alicea as he bounds around the room, sitting on people as they do push-ups, and squatting like a frog as he cheers them on.

“We are Angel groupies,” says Anna Luscombe, a 27-year-old British expat who’s been taking the class since it started in February. “He pushes us to another level. You literally want to throw up in his class.”

All around the city, from 70 people waiting to enter a yoga class at Jivamukti, to a stoked set of Upper East Siders shelling out $32 per class at spiritual spinning studio Soul Cycle, New York workout enthusiasts are so passionately devoted to a new crop of exercise classes that they’ll schedule their lunch hour around them or wait on hour-long lines to get in, as if they were the hottest nightclub in town.

“I’m psycho; I work out almost every day,” says Sarabeth Turner, a 28-year-old freelance photographer, who splits her workouts between Physique 57, a controlled class emphasizing corps strength, and Flywheel, a spinning studio started by Soul Cycle co-founder Ruth Zuckerman and NFL star Tiki Barber. “A little while ago I had an injury, and when I was told I couldn’t work out for two months, I had to literally pray in church that I could find the same kind of peace of mind.”

Of course, stress relief has always been a key factor in the addiction to exercise. “I feel like my head is a clogged drain, and the class is Drano,” she adds.

In New York, where it’s easy to feel like an outsider, fitness studios also establish a sense of community and identity. “It’s the ‘Cheers’ effect,” says Dechen Thurman, the 37-year-old brother of Uma, whose classes at Jivamukti draw crowds. “People like to walk into a place and be known.”

His class has a decidedly different identity from Angel’s, but the participants are just as bonded in their like-mindedness.

After class, friends often gather in the studio’s café. “I’d be frustrated and depressed if I couldn’t come to yoga,” says 39-year-old Karina Muller-Evill. “I’m dealing with people all day, but I can disconnect here.”

The community is a bit more testosterone-fueled at Flywheel, where 48-year-old Wayne Edelman spins with wife Merritt every day, sometimes twice a day.

“We used to go to Soul Cycle,” says Edelman, “but it was so packed that I had to change on the street. I remember one day a woman was going up to the front desk, where they have candles burning for atmosphere. It was so crowded that her hair caught fire. It was also costing about $1,800 per month for us to spin there.”

The privilege of being in a place where people happily fork over high tariffs for membership, and the thrill of racing to secure a coveted spot in a class, is part of the appeal of Soul Cycle and Physique 57. “It’s like the club you can’t get into that you want to get into,” observes Zuckerman.

“My friends and I sign up months ahead so that we can get the classes we want,” notes Lori Silverstein, who goes to Physique 57 daily. Members even have the option of paying nearly double for a guaranteed seat.

Over at Alvin Ailey, where teens and septuagenarians take Samuel Salazar’s Zumba, camaraderie is as much of a draw as the workout. “It’s the friendships that keep me coming back,” says 49-year-old Wendy Williams, a yoga teacher who’s found her true affinity in the salsa-style classes. “It’s my priority. Everything in my life is worked around Zumba.”

Meaghan Joynt, 35, who lost 90 pounds taking Zumba, agrees: “I get very emotional when I talk about his class. It’s a special community.”

Crunch instructor Mario Godiva Green, who teaches a class called Boing with Kangoo, where students wear boots that resemble roller blades with a large spring instead of wheels, also has dedicated students.

“I bought my own boots, because if you don’t have your own and you don’t get to class really early, you get shut out,” says Max Schneider, 23. “If I miss class, I’m angry and disappointed.”

Another aspect of a class’s appeal to New Yorkers is the ability to give up control. “A lot of my students are bosses,” says Tabata’s Angel.

“In my class, I’m the boss. All they have to worry about is doing what I ask. This town can eat you up, and my class makes them strong. I don’t mean just physically. Our mind is the most powerful muscle in the body.”

Fitness for fanatics

FOR TRENDSTERS

*Boing With Kangoo, at Crunch, 113 Fourth Ave., Thursday at 8:15p.m.

In Marion Green’s fun class, students bounce around on skates (above) using leg strength and balance to execute the steps.